Laminated structures and method of making same



Patented Oct. 2, 1956 United States Patent ()fiice LAMINATED STRUCTURESAND METHOD OF MAKING SAME Lucille E. Williams, Wilmington, Del.,assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., acorporation of Delaware N Drawing. Application August 31, 1954, SerialNo. 453,440 11 Claims. (Cl. 154-139) This invention relates to laminatedstructures, more particularly to such structures comprising laminae of ah ydrophobic layer adhered to a polymeric linear terephthalate esterlayer by means of a copolyester layer, and processes of making suchstructures.

This application is a continuation-in-part of my ct pending applicationSerial No. 419,103 filed March 26, 1954.

U. S. Patent 2,465,319 describes a process for the preparation of highlypolymerized linear esters of terephthalic acid and glycols of the seriesHO(CH2)nOH, where n is a whole number Within the range of 2 to 10. Thesepolymeric esters may be spun into filaments and then woven into textilefabrics. They may be cast from organic solution to prepare unsupportedfilms. A hot plastic mass of the polymeric linear terephthalate estersmay be formed into unsupported films by passing the mass between smoothhot calender rolls or melt casting from a hopper.

For certain applications it is desirable to laminate a film or fabricprepared from the polyester described in U. S. Patent 2,465,319 toitself in a variety of constructions, such as, e. g. film to film,fabric to fabric and fabric to film. Also it is desirable to adhere thepolyethylene terephthalate film or fabric to chemically dissimilarhydrophobic surfaces such as nylon, glass, polyacrylonitrile, vinylidenepolymers, such as, e. g., polyvinylidene chloride and vinyl chloridepolymers as well as copolymers and various metals. Conventionaladhesives do not adhere to the polyethylene terephthalate.

Throughout the specification and appended claims the term polymericlinear terephthalate ester refers to an oriented highly polymerizedlinear ester of terephthalic acid and a glycol of the series HO(CH2)nOH,where n is a whole number within the range of 2 to 10.

I It is an object of this invention to provide laminated structuresinvolving at least one layer of a polymeric linear terephthalate esterand another hydrophobic layer withan intermediate layer of a copolyesterdefined here inafter. Another object is the provision of a process foruniting-a polymeric linear terephthalate ester to itself or otherhydrophobic surfaces by means..of a copolyester adhesive composition.

The objects of this invention are accomplished by laminating a sheet ofpolymeric linear terephthalate to itself or chemically dissimilarhydrophobic surfaces by means of a composition comprising a copolyesterof at least one acyclic dicarboxylic acid and at least one symmetricalaromatic dicarboxylic acid with a polymethyleiie glycol of the formulaHO(CH2)7LOH, where n is a whole number from 2 to 6 inclusive.

The polymeric linear terephthalate ester referred to in the followingspecific examples may be prepared in accordance with the teaching setforth in U. S. Patent 2,465,319 issued March 22, 1949, to I. R.Whinfield et al.

The copolyesters employed for bonding to the polymeric linearterephthalate are similar to those prepared by copolymerizing under meltpolymerization conditions, within certain composition limits hereinafterset forth, at least one acyclic dicarboxylic acid of the formula 2wherein X is a linear chain composed of 4 to 9 atoms, in the chain ofwhich not more than three may be oxygen atoms and the remaining arehydrocarbon carbon atoms, any two such oxygen atoms being separated byat least two such carbon atoms, the hydrocarbon carbon atoms beingsaturated and containing a total of not more than three hydrocarboncarbon atoms as side chain substituents, with at least one symmetricalaromatic dibasic acid from the group consisting of terephthalic acid,bibenzoic acid, ethylene bis p-oxybenzoic acid, tetramethylene bisp-oxybenzoic acid and 2,6-naphthalic acid and with a polymethyleneglycol of the formula HO (CH2)nOH wherein n is a Whole number from 2 to6 inclusive.

To make the copolyesters for the purpose of this invention, it isnecessary that the aromatic acid comprise at least 30% and not more than90% by weight of the total acid component of final polymer. A preferredrange is 55-80% of the aromatic acid. It is a simple matter to obtainany desired ratio of acid components in any one copolyester. the finalpolymer in the same ratio as they were present in the initial reactants,provided an excess of glycol is used. It should be understood, ofcourse, that many combinations of these aliphatic and aromatic acids maybe used. Thus, two or more aliphatic and/or two or more aromatic acidsmay be used to form the copolyester. It is also to be understood thatthe ester-forming derivatives of these acids can be used in place of,and are the full equivalents of, the acids described above, as isgenerally the case in the manufacture of linear polyesters. Thecopolyesters per se are the invention of M. D. Snyder and are disclosedand claimed in U. S. Patent 2,623,033, issued December 23 1952.

The melt mixtures of polyesters and copolyesters described in U. S.Patent 2,623,031, issued December 23, 1952, to M. D. Snyder, may also beused to adhere to a surface of the polymeric linear terephthalate ester.The

ester described above and thereafter melt-blending the copolyester thusformed with an aromatic polyester prepared by'melt polymerizing asymmetrical aromatic dibasic -acid, from the group consisting ofterephthalic acid, bibenzoic acid, tetramethylene bis p-oxybenzoic acid,and 2,6-naphthalic acid, and a polymethylene glycol of the formulaHO(CH2)11OH, n being a whole number from 2 to 6 inclusive. Preferably,the same aromatic dibasic acid used in the-copolyester is used in thepolyester. As in the case of'th'e copolyester, the aromatic acidcomponent of the melt-blend of the polyester and copolyester should beat least 30% and not more than 90% on a weight basis. 9

The following specific examples are given by the way of illustration andnotlimitat-ion. The parts and percentage figures throughout thespecification and claims 3 are expressed ona weight basis.

I Example I -A pellicle of polymeric linear terephthalate, 1 mil thick,

, was coated on one side with a-thin layerof the following adhesivecomposition:

, Parts by weight Copolyester of 60 parts of ethylene terephthalate and40 parts of ethylene sebacate 16.7 Chloroform 83.3

Sufiic-ient composition was applied to deposit about .5 ounce per squareyard of dry coating. After the solvent was evaporated from the adhesivelayer, the dry adhesive The acids will be present in coating was doubledupon itself to form two plies of film with adhesive sandwiched between.The doubled film was then hot pressed at 160190 F. for about minutes at500 pounds per square inch. After cooling to room temperature theadhesion of the two plies of film was found to be 7.5 pounds per oneinch strip.

Example II A woven polyethylene terephthalate fabric weighing about 3.0ounces per square yard, having a thread count of 112 x 83 (warp xfillerthreads/ inch) was coated on one side with the adhesivecomposition of Example I and then heated to evaporate the solvent. Thedry adhesive film was about 1 mil thick. A pellicle of polyethyleneterephthalate .5 mil thick was superposed over the dry adhesive on thewoven fabric and the assembly passed between pressure rolls heated toabout 300 F. After cooling to room temperature the laminated assemblywas subjected to the standard adhesion test by fastening one inch stripsof unlarninated portions of the assembly in the opposite jaws of a Scotttester and then measuring the pull required to separate the plies at auniform rate. The .5 mil film one inch wide broke at 13.0 pounds pullwithout any separation of the. laminated portion of the assembly.

Example III Wyzenbeek abrasion resistance (using 240 I 4000 strokes.

abradinz surface).

Tensile strength 143 lbs. Tensile strength, after 48 hour immersion in132 lbs;

sulfuric acid. Tensile strength, after 48 hour immersion in 135 lbs.

benzene. Tensile strength, after 48 hour immersion in 132 lbs.

gasoline. Teinsile strength, after heating at 250 F. for 7 115 lbs.

ays. Dielectric strength 947 volts/mil. Hydrostatic resistance, filmside next to water 228-260 lbs. Heat resistance, after 30 day exposureat 250 F; No deterioration.

Resistance to cracking on sharp foldz Greased in warp direction- Nocgacking at minus Greased in filler direction No cgacking at minus 100 IScrub test, dr No cracking after 500 7 cycles. Scrub test, after 24 hourimmersion ina solvent No cracking after 500 mixture of: Dilsobutylene,60%; benzene, 5%; cyclestoluene, xylene, 15%. Schiltknecht flex..-37,500flexes. After 48 hour exposure to ozone N3 cracking or degra-.

' ation. Benzene vapor permeability None. High octane zasolinevaporpermcability None.

Benzene liquid permeability None. Highoctane gasoline liquidpermeability 2.

The Wyzenbeek abrasion resistance test was carried out in accordancewith Method 5304 of Federal Specification. CCC-T-19lb TextileTestMethods dated May 15, 1951.

The tensile strength tests werecarried out on a Scott tester using a 50pound weight on side arm.

The dielectric strength test was carried out in accordance with theAS'DM D149-44 short time test in air, electrode with 60 cyclealternating current.

The hydrostatic test was carried out in accordance with Mullen ASTMD751-46T test.

The scrub test was carried out on an apparatus similar to thatillustratedin Automotive Industries 49, p. 1262-6.

The Schiltkuecht flex test was carried out in accordance with test and.

apparatus described in Bulletin #105, published by Alfred Suter, 200Fifth Avenue, New York, N. Y.

The benzene vapor and liquid permeability tests were carried out by placng 150 g. of benzene in a pint Mason'jar. The test specimen of thelaminated material was used as the sealing gasket for a two piece screwtop lid with the linear polyethylene tercphthalate surface toward theliquid. For the Vapor permeability test the jars remained upright andfor the liquid permeability test the jars were turned upside down sothat the liquid contacted the test specimen. The numerical valuesreported above are the grams weight of the loss of liquid after 7 daysat room gggnpeggtpure. The test is similar to the procedure described inA STM 4 Example IV A two mil thick film of a copolyester of 60 parts ofethylene terephthalate and 40 parts of ethylene sebacate was sandwichedbetween a layer of ECC111 12 Fiberglas and a layer of mil thick pellicleof polyethylene terephthalate. The assembly was subjected to a pressureof about pounds per square inch at 307 F. for 10 minutes. The finalproduct had a thickness of 4. mils and was flexible. The dielectricstrength was as high as 2000 volts per mil thickness. In an attempt todetermine the bond strength of the laminate the glass fabric tore beforeany stripping occurred.

A two mil thick film of a copolyester of 60 parts of ethyleneterephthalate and 40 parts of ethylene sebacatc. was superposed over awoven polyethylene terephthalate fabric such as described in Example 11.The assembly was subjected to a pressure of about 500 pounds per squareinch at 307 F. for 10 minutes. The two plies were firmly united togetherto form a composite assembly.

Example VI A 1 mil thick pellicle of polyethylene terephthalate was.coated on one side with the following composition:

Parts by weight Copolyester of about 65 parts of ethylene ter-.

Example ephthalate and 35 parts of ethylene sebacatc 22.5

Heat reactive para tertiary butyl phenol/formaldehyde resin 7.5 Acetone70.0- 100.0

Example VII A hot melt of a copolyester of 30 parts of ethyleneterephthalate and 70 parts of ethylene sebacate-was spread" uniformly ona thin film of polyethylene terephthalate. The-coated side of the filmwas immediately double uponitself-and the assembly was then hand pressedwith a sealing iron at about 194 F; Excellent adhesion was obtainedbetween the two plies of the polyethylene terephthalate film.

Example VIII A twomil thick film of a copolyester-of 60 parts; Offethylene. terephthalate. and 40 parts of ethylene sebacate. wassandwiched between a one mil thick film of poly-.ethyleneterephthalate.and a nylon parachute fabric weigh; ing about 1.8ounces per square yard. The assemblywas; subjected to a pressure ofabout 500 poundsper-square; inch and a temperature of about 307 F. for;10 minutes.

After cooling toroom temperature the adhesi on ofithe polyethylenete'rephthalate to the nylon fabric wa s ;foun dl to be 4.0 pounds perone inch strip.

Example IX Example VIII was repeated with fabricwoven from yarnscomposed ofpolyacrylonitrile in place of the nylon fabric.

The adhesion of the polyethylene terephthalate film; to thepolyacrylonitrile fabric was 4.0 pounds per one inch strip.

Examples X to XV A one mil thick preformed film of a copolymercomprising 60 parts of ethylene terephthalate and 40 parts of ethylenesebacate was interposed between a three mil thick film of polyethyleneterephthalate and another lamina, as indicated in the table below. Theassemblies were preheated for 1.5 minutes at 302 F. and then subjectedto a pressure of about 3000 pounds per square inch for an additional oneminute at the same temperature. The laminates were removed from thepress and allowed to cool to room temperature. The bond strengths of thelaminates were tested and the following results were obtained:

1 Only slight hand pressure applied after heating the assembly for 2.6minutes at 302 F.

Example XVI A cotton fabric running 2.40 yards per pound per 60 inchwidth was coated with 13.0 ounces per square yard of a plastisolcomposition of the following approximate formula:

Parts by weight Polyvinyl chloride powder 49.4 Dioctyl phthalate 30.6Pigments and filler 20.0

The polyvinyl chloride powder, pigments and filler were dispersed in thedioctyl phthalate at room temperature to form a paste-like composition,known as a plastisol. The polyvinyl chloride powder is dispersed asundissolved particles. The plastisol was spread on the fabric by meansof a doctor knife, in a single coat, after which it was passed through aheat zone (325-375 F.) which fused the plastisol to a tough coatinghaving high mechanical strength when cooled to room temperature. Apreformed film of a copolyester of 60 parts of ethylene terephthalateand 40 parts ethylene sebacate 5 mils thick was sandwiched between thepolyvinyl chloride coating and a preformed film of polymeric linearterephthalate ester 5 mils thick. The assembly was preheated for oneminute at 300 F. before subjecting to a pressure of 600 p. s. i. for aperiod of one minute at 300 F.

The adhesion of the polymeric linear terephthalate ester film to theassembly was 12.0 lbs. per one inch strip. The product was glossy andhad the appearance of patent leather. The glossy surface was scuffresistant. It was adaptable for footwear, ladies handbags, belts,millinery and novelty products.

The adhesion tests employed in all the examples were carried out inaccordance with the procedure described in Method 5950 of FederalSpecification CCC-T-l9lb dated May 15, 1951, and entitled Textile TestMethods.

The copolyesters may also be used to adhere the polymeric linearterephthalate ester to the non-woven webs described in U. S. Patent2,676,128, issued April 20, 1954, to J. A. Piccard and copendingapplications S. N. 267,911, now abandoned, and S. N. 267,912, filedJanuary 23, 1952, and S. N. 232,247, filed June 18, 1951, by E. A.Rodman, now Patent No. 2,725,309.

A plurality of plies of alternating layers of the polymeric linearterephthalate and copolyester may be sub; jected to heat and pressuretomake rigid and'semi-rigicl laminates.

Due to the high strength of the polymeric linear terephthalate, films asthin as .25 mil are satisfactory for the purpose of this invention.There are no particular limits for the thickness of the polymeric linearterephthalate films in carrying out this invention. Economicconsiderations will usually control the upper limit of thickness of thepolymeric linear terephthalate films. Likewise there are no particularlimits on the weight or construction of the polymeric linearterephthalate fabrics in carrying out this invention. The polymericlinear terephthalate fabric may be woven or non-woven.

In place of the polyethylene terephthalate used in the specificexamples, it is to be understood that the highly polymerized estersobtained by the reaction of terephthalic acid and polymethylene glycolshaving more than 2 but not more than 10 methylene groups may also beused in this invention; such as, e. g. trimethylene glycol,tetramethylene glycol, pentamethylene glycol, hexamethylene glycol,heptamethylene glycol, octamethylene glycol, nonamethylene glycol, anddecamethylene glycol. 'Ihe glycols having 2 to 4 methylene groups arepreferred.

The phenol-aldehyde resin employed with the copolyester in the bondinglayer of Example VI is preferably thermosetting or heat reactive, i. e.,capable of hardening or curing when heated. The resin may be made byreacting any of the phenols with any of the aldehydes, preferably thealiphatic aldehydes. The phenol may be cresol, phenol, Xylenol andresorcinol, as well as substituted phenols such as, e. g. para tertiarybutyl phenol, para ter-' tiary amyl phenol, para phenyl phenol, or paraoctyl phenol. The phenolic resins may be modified with drying oils,semi-drying oils, rosin and similar materials. Such resins areobtainable on the open market under the proprietary names of Amberlite,Bakelite, Beckacite, Catalin, Durez, Indur, Resinox and Texolite. Theheat reactive phenol-aldehyde resin may be present in the adhesivecomposition in amounts up to 50% of the weight of the copolyester.

The copolyester adhesive composition may also be used as an adherentsurface coating to the polymeric linear terephthalate esters in film orfabric form, in which case J it may be desirable to add coloringmaterials, such as pigments and dyes, to the surface coating. Such acoating may be a continuous overall coating or it may be used as aprinting or stencil ink, in which case the coating is applied in theform of designs on only a portion of the surface to be coated.Furthermore, the adhesive composition may be employed as a coating foranchoring various moistureproofing coatings, e. g., polyvinyl chloride,polyvinylidene chloride and copolymers thereof, to polymeric linearterephthalate esters in film form.

In some cases, it may be desirable to add a plasticizer to the adhesivecomposition, and for this purpose the following materials may beemployed; sebacic or phthalic diester of monobutyl ether of ethyleneglycol, tricresyl phosphate, triphenyl phosphate, dioctyl phthalate,dibutyl phthalate and dibutyl sebacate.

The products of this invention have unusual resistance to both aromaticand aliphatic hydrocarbon liquids which make them particularly useful ascarburetor and fuel pump diaphragms, gasoline hose interiors, printersblankets, covering for electrical cables and gaskets requiringhydrocarbon resistance.

It is apparent that many Widely different embodiments of this inventioncan be made without departing from the spirit and scope thereof and,therefore, it is not intended to be limited except as indicated in theappended claims.

I claim:

1. A laminated assembly comprising at least three layers, (1) the firstof which consists of polymeric linear terephthalate ester, (2) as anintermediate layer a copolyester of an acyclic dicarboxylic acid of theformula whereX is a linear chain composed of 4 to 9 atoms, in the chainof which not more than three may be oxygen atoms and the remaining arehydrocarbon carbon atoms, any two such oxygen-atoms being separated byat least two such carbon atoms, the hydrocarbon carbon atoms beingsaturated and containing a total of not more than three hydrocarboncarbon atoms as side chain substituents; and (b) at least onepolymethylene glycol ester of a symmetrical arom'atic dibasic acid fromthe group consisting of tereph- V 3. The product of claim 1 in which thefirst mentioned polymeric linear terephthalate ester is in the form of afabric.

, 4. The product of claim 1 in which the intermediate layer (2) alsocontains a heat reactive phenolaldehyde resin.

5. The product of claim 4 in which the intermediate layer (2) containsup to 50% of the weight of. the copolyester.

. 6. The method of preparing laminated assemblies whichcomprisesadhering the surface of a polymeric linear terephthalate ester to acopolyester, said copolyester comprising (a) at least one polymethyleneglycol ester of an acyclic dicarboxylic acid of the formula atoms andthe remaining are hydrocarbon carbon atoms, any two such oxygen atomsbeing separated by at least two such carbon atoms, the hydrocarboncarbon atoms being saturated and containing a total of. not more thanthree hydrocarbon carbon atoms as side chain substituents, and (b) atleast one polymethylene glycol ester of a symmetrical aromatic. dibasicacid from the group consisting of terephthalic acid, bibenzoic acid,ethylene bis p-oXy-benzoic acid, tetramethylene bis p-oXy-benzoic acid.

and 2,6-naphthalic acid, the aromatic acid comprising.

from to 90% by weight of the acid components of the copolyester, and thepolymethylene glycol component of {a} and (1')) having from 2 to 6carbon atoms, and adhering to said copolyester layer a hydrophobic layerselected from the group consisting of polymeric linear terephthalateester, polyacrylonitrile, vinylidene chloride polymer, vinyl chloridepolymer and nylon.

7. The method of claim 6 in which the first mentioned polymeric linearterephthalate ester is in the form of a film.

8. The method of claim 6 in which the first mentioned polymeric linearterephthalate ester is in the form of a fabric.

9. The method of claim 6 in which the'copolyrner is applied to thepolymeric linear terephtha'late ester surface in the form of adispersion of the copolyester in an organic solvent.

10. The method of claim 6 in which the copolyester is applied to thepolymeric linear terephthalate ester surface in the form of a hot melt.

11. The method which comprises adhering a polymeric linear'terephthalateester surface to another surface which comprises interposing a preformedfilm of the copolyester of claim 6 between the surface of said polymericlinear terephthalate ester and said other surface, and subjecting theassembly to heat and pressure, said other surface being a hydrophobiclayer selected from the group consisting of polymeric linearterephthalate ester, polyacrylonitrile, vinylidene chloride polymer,vinyl chloride polymer and nylon.

References Cited in the file of this patent UNITED STATES PATENTS2,623,031 Snyder Dec. 23, 1952 2,623,033 Snyder Dec. 23, 1952 2,673,826Ness Mar. 30, 1954 2,676,128 Piccard Apr. 20, 1954

6. THE METHOD OF PREPARING LAMINATED ASSEMBLIES WHICH COMPRISES ADHERINGTHE SURFACE OF A POLYMERIC LINEAR TEREPHTHALATE ESTER TO A COPOLYESTER,SAID COPOLYESTER COMPRISING (A) AT LEAST ONE POLYMETHYLENE GLYCOL ESTEROF AN ACYCLIC DICARBOXYLIC ACID OF THE FORMULA